Closed loop combine cleaning fan control

Abstract

A cleaning system of a combine harvester includes a fan, a first valve member positioned within a first duct of the fan for throttling the flow of air through the first duct, a second valve member positioned within the second duct of the fan for throttling the flow of air through the second duct, a first actuator for adjusting a position of the first valve member, a second actuator for adjusting a position of the second valve member, first and second sensors for sensing air pressure at first and second sieves, and a controller. The controller is configured to receive the sensed air pressures from the sensors, compare the sensed air pressures with either each other or threshold values, and transmit instructions to one or both of the actuators to adjust the positions of one or both of the valve members.

What is claimed is: 
     
       1. A cleaning system of a combine harvester comprising:
 a fan assembly comprising a housing, a fan rotor at least partially positioned within the housing, at least one inlet duct through which air is delivered into the housing, a first duct leading to a first outlet port through which air is exhausted outside of the housing, a second duct leading to a second outlet port through which air is also exhausted outside of the housing, and a stationary partition disposed between and at least partially forming the first and second ducts; 
 a first valve member positioned within the first duct for throttling the flow of air through the first duct; 
 a second valve member positioned within the second duct for throttling the flow of air through the second duct; 
 a first actuator for adjusting a position of the first valve member within the first duct; 
 a second actuator for adjusting a position of the second valve member within the second duct; 
 a first sieve positioned adjacent the first outlet port to receive a flow of air from the first duct; 
 a second sieve positioned adjacent the second outlet port to receive a flow of air from the second duct; 
 a first sensor for either directly or indirectly sensing an air pressure at the first sieve; 
 a second sensor for either directly or indirectly sensing an air pressure at the second sieve; and 
 a controller for receiving the sensed air pressures from the first and second sensors, comparing the sensed air pressures with either each other or threshold values, and transmitting instructions to both of the first and second actuators to adjust the positions of both of the first and second valve members based upon the comparison and thereby equalize the flow of air through the first and second ducts toward the first and second sieves, respectively. 
 
     
     
       2. The cleaning system of  claim 1 , wherein each sieve includes openings through which grain can pass. 
     
     
       3. The cleaning system of  claim 1 , wherein the first sensor is mounted to a housing for the first sieve, and the second sensor is mounted to a housing for the second sieve. 
     
     
       4. The cleaning system of  claim 1 , wherein the first sensor is at least partially positioned within the first duct, and the second sensor is at least partially positioned within the second duct. 
     
     
       5. The cleaning system of  claim 1 , wherein each sensor is a pressure transducer, a pressure switch, or a strain gauge. 
     
     
       6. The cleaning system of  claim 1 , wherein each valve member is pivotably connected to the housing of the fan assembly. 
     
     
       7. The cleaning system of  claim 1 , wherein the first sensor is positioned directly below the first sieve, and the second sensor is positioned directly below the second sieve. 
     
     
       8. The cleaning system of  claim 1 , wherein the first sensor is positioned downstream of the first valve member, and the second sensor is positioned downstream of the second valve member. 
     
     
       9. The cleaning system of  claim 1 , wherein the sieves form part of a cleaning shoe. 
     
     
       10. The cleaning system of  claim 1 , wherein the controller employs a PID loop for adjusting the position of the first and/or second valve members until the sensed air pressures arrive at predetermined values. 
     
     
       11. The cleaning system of  claim 1 , wherein the controller is configured to adjust the position of the first and/or second valve members until the sensed air pressures are either equivalent or a difference between the sensed air pressures is maintained within a predefined threshold. 
     
     
       12. A combine harvester comprising the cleaning system of  claim 1 . 
     
     
       13. The combine harvester of  claim 12  further comprising a rotor and concave that are positioned at an elevation above the cleaning system. 
     
     
       14. The cleaning system of  claim 1 , wherein the stationary partition is disposed between the first and second valve members. 
     
     
       15. A method for operating a cleaning system of a combine harvester, said method comprising:
 receiving, at a controller, air pressure measurements from first and second pressure sensors located either at or near first and second sieves of the cleaning system; 
 comparing, using the controller, the air pressure measurements with either each other or threshold valves; and 
 adjusting a position of first and second valve members within first and second ducts of a fan housing of the cleaning system, respectively, by way of the controller, to change equalize a flow of air through the first and second ducts toward the first and second sieves, respectively. 
 
     
     
       16. The method of  claim 15 , further comprising, following the adjusting step, receiving, at the controller, further air pressure measurements at the first and second sieves of the cleaning system. 
     
     
       17. The method of  claim 15 , wherein the first sensor is mounted to a housing for the first sieve, and the second sensor is mounted to a housing for the second sieve. 
     
     
       18. The method of  claim 15 , wherein the first sensor is at least partially positioned within the first duct, and the second sensor is at least partially positioned within the second duct. 
     
     
       19. The method of  claim 15 , wherein each valve member is pivotably connected to the fan housing. 
     
     
       20. The method of  claim 15 , wherein the method comprises operating the cleaning system while threshing grain using a rotor and concave of the combine harvester. 
     
     
       21. The method of  claim 15 , wherein the fan housing comprises a stationary partition that (i) is disposed between and at least partially forms the first and second ducts and (ii) is disposed between the first and second valve members.